The symbiose between carapid fishes and holothuroids around Laing Island (Sea of Bismarck, Papua New Guinea).The occurrence of carapid fishes have been investigated in twenty species of holothuroids in the vicinity of Laing Island. Infestation was demonstrated in five species only, viz. Bohadschia argus, Holothuria (Metriatyla) ocellata, Pearsonothuria graeffei, Thelenota ananas, Stichopus horrens. A total of 114 carapids belonging to three different species (Carapus homei, Carapus parvipinnis, Encheliophis (Jordanicus) gracilis) were collected, 107 of them having been found in either the right respiratory tree or the general body cavity of the species B. argus. Up to 4 carapids were found in a single B. argus. The carapid-B. argus symbiose is considered to be commensalism, the holothuroids host providing a well-protected and well-oxygenated shelter to its carapid symbiote. B. argus never expels its Cuverian tubules when penetrated by a carapid which implies the occurrence of particular adaptations developed by the infesting symbiote.